FIG. 1 shows a configuration disclosed in Patent Literature 1 as an example of a conventional brushless resolver. This brushless resolver includes a ring-shaped resolver 13 disposed in a cylindrical case 12 that covers a rotation-center shaft 11, a ring-shaped rotation transformer 20 disposed side by side with the resolver 13, and lead wires 27 electrically connected to the resolver 13 and to the rotation transformer 20.
The resolver 13 is composed of a resolver rotor 14 that is rotatable around the shaft 11 and a resolver stator 17 fixed to the cylindrical case 12. The resolver rotor 14 is configured by winding resolver-rotor windings 16 around resolver-rotor iron cores 15. The resolver stator 17 is configured by winding resolver-stator windings 19 around resolver-stator iron cores 18.
When the resolver 13 is a one-phase excitation and two-phase output resolver, the resolver-rotor windings 16 are made of one-phase distributed windings, and the resolver-stator windings 19 are made of two-phase distributed windings (sin windings and cos windings) separated from each other by an electrical angle of 90 degrees. In the resolver 13 having such a configuration, when the resolver rotor 14 is excited by an excitation signal sent from the rotation transformer 20, two signals corresponding to the rotation angle are generated on the resolver stator 17 side, and the rotation angle can be calculated from the two signals.
The rotation transformer 20 is composed of a rotor transformer 21 that is rotatable around the shaft 11 and a stator transformer 24 fixed to the cylindrical case 12. The rotor transformer 21 is composed of a ring-shaped rotor-transformer iron core 22 and a rotor-transformer winding 23 of a multiwinding magnet wire wound in the circumferential direction of the rotor-transformer iron core 22. The stator transformer 24 is composed of a ring-shaped stator-transformer iron core 25 and stator-transformer windings 26, the stator-transformer windings 26 being multiwinding magnet wires wound around bobbins disposed in the stator-transformer iron core 25 and wound in a bobbin's circumferential direction.
When the rotation transformer 20 is configured in this manner, an excitation signal electrically sent via a lead wire 27 to the stator transformer 24 is transferred to the rotor transformer 21 side in a noncontact manner as a voltage signal corresponding to the winding ratio between the stator-transformer windings 26 and the rotor-transformer windings 23. Then, this excitation signal is electrically sent to the resolver-rotor windings 16 of the resolver rotor 14 connected to the rotor transformer 21, thereby allowing the rotation position to be detected by the resolver 13.